Coated cemented carbides for brazing

ABSTRACT

A coated cemented carbide and method for making same are disclosed, wherein the binder metal and coating metal are the same and is one of iron, cobalt or nickel, and wherein the coated cemented carbide shows improved wettability to facilitate brazing. Coating by vapor deposition and sulfamate bath electroplating are disclosed as being preferred methods. Cemented carbide discs treated according to this method are suitable for brazing for use in automotive valve lifter assemblies.

United States Patent Kalish Oct. 28, 1975 1 COATED CEMENTED CARBIDES FOR3,258,817 7/1966 Smiley 22/202 BRAZING 3,348,967 10/1967 Hucke 117/118[75] Inventor: Herbert S. Kalish, Short Hills, NJ.

[73] Assignee: 'Adamas Carbide Corporation, Kenilworth, NJ.

Filed: Jan. 23, 1974 21 Appl. No.2 435,737

52 US. Cl. 29/195 51 v Int. C1 B32B 15/04 58 -Fi e1d of Search 29/195 A,182.1, 182.7,

Montgomery 29/19 1.2

Primary Examiner-L. Dewayne Rutledge Assistant Examiner-E. L. Weise IAttorney, Agent, or FirmMarvin Feldman; J. B. Felshin 1 57 j ABSTRACT 12No Drawings COATED CEMENTED CARBIDES FOR BRAZING This invention relatesto coating the surface of a cemented carbide to improve wettability soas to facilitate brazing.

Refractory carbide hard metals or cemented carbides are sinteredproducts consisting primarily of carbides of tungsten, titanium and/orother refractory carbides cemented together by liquid phase sinteringusing a matrix metal, such as cobalt, nickel or iron as the binder.These cemented carbides exhibit desirable properties as they are bothhard metals further strengthened by the presence of the binder metal.

It is desirous to join cemented carbide parts to other metal parts suchas ferrous metals, by brazing. It is well known that difficulties may beexperienced by brazing, because owing to the composition of the cementedcarbide the surfaces are not easily wetted in the brazing process.

Heretofore it was known to provide a wettable layer of a metal, metalalloy or metal salt on a cemented carbide to facilitate brazing. Variousmetals, alloys and salts have been employed with varying degrees ofimproved wettability. One conventional method is the salt bath treatmentfor coating carbide part to facilitate brazing. Attempts to nickel platea cemented carbide having a cobalt binding did not achieve the desiredlevel of wettability.

It is therefore an object of this invention to provide a coated cementedcarbide with improved wettability to facilitate brazing.

It is further an object of this invention to provide a method of coatinga cemented carbide to improve wettability so as to facilitate brazing.

It is further an object of this invention to provide a method asaforesaid wherein the need for cleaning the cemented carbide prior tocoating is minimized.

It is still a further object of this invention to provide a high puritymetal coating on a cemented carbide wherein the binder metal is the sameas the coating metal.

It is a further object of this invention to provide a method fortreating thin cemented carbides discs to facilitate brazing to a metalpart.

It is still a further object of this invention to provide a coatedcemented carbide as aforesaid which is inexpensively produced and is yetpractical in use for brazing to other materials.

Now, therefore there is disclosed herein a coated cemented carbide forimproved wetting to facilitate brazing wherein it is recognized that thebinder metal of the cemented carbide be the same metal as the layer ofmetal deposited on the surface. It has also been found that whereas theprior art wettable layers were alloys or salts of certain metals, thepresent invention finds that a high purity metal coat provides goodwettability. It has been further found that specific coating methods,particularly, vapor deposition by the electron beam technique and mostpreferrably, electrodeposition from a metal sulfamate bath, provide thedesired high purity coated cemented carbides exhibiting improvedwettability properties.

It has also been found that whereas certain prior art brazing techniquesrequired extensive cleaning of the cemented carbide parts, byparticularly abrasive methods, such as sand blasting, tumbling or thelike, the presently described coating methods, particularly thattungsten carbide cobalt binder EXAMPLE I Fifty (50) cemented carbidetest discs were coated with cobalt by painting the disc with a mixtureof fine cobalt power, powdered Lucite and flux in a toluene solvent. Theaforesaid painted pieces were heat treated in a hydrogen atmospherefurnace at 1 C. The first test set is designated as A.

The second set of fifty (50) cemented carbide test discs were treated bythe salt bath treatment. The salt bath treatment employed is generallythat as disclosed in US. Pat. No. 2,979,811 granted Apr. 18, 1961. Thesecond set is designated at B.

A third set of fifty (50) cemented carbide discs were electroplated in acobalt sulfamate bath to deposit a coating of cobalt on the discs, aswill be described more fully hereinafter. This third set is designatedas C.

A fourth set of fifty (50) cemented carbide test discs were coated witha layer of cobalt metal by vapor deposition employing an electron beamcoating technique. This fourth set is designated as D.

After heat treatment a small piece of copper was placed on top of thepieces, for each of the sets, and the pieces were then put through ahydrogen furnace at 1150C; the melting point of the copper being 1083C.

The results of the wettability for each of the lots is as follows:

EXAMPLE n A set of titanium carbide discs having a nickel binder metalwas coated with a layer of nickel metal employing the sulfamate bathelectrodeposition technique. The coated cemented carbides wettedsuccessfully.

In the sulfamate electroplating method, it has been found that similaroperating conditions may be employed for nickel and cobalt because ofthe similarity in electrochemical characteristics of these metals.

Prior to electroplating, the discs are first cleaned to remove soil oroily film so as to ensure adequate adhesion of the cobalt metal.Electrocleaning employing an alkaline cleaner is the preferred method.Abrasive cleaning is unecessary. After cleaning, the discs are thenrinsed in an air agitated rinse tank using deionized water. Afterrinsing, a dilute acid dip is employed to neutralize any alkalineresidue on the surface of the discs.

The discs are then placed in a cobalt sulfamate or nickel sulfamatebath, depending of course on the binder metal, having a concentration of225 grams metal per liter; a pH of about 4.0; at 25C. A suitable currentdensity is about 40 amps/sq. ft. The cobalt sulfamate bath is airagitated.

At 40 amps/sq. ft., a metal coat of about 0.00025 inch will deposit outin about 8 minutes. Discs are plated to layers of about 0.0002 inch toabout 0.0004 inch. Other parts, such as cutting tips have been similarlyplated to thickness of from about 0.1 mil to about 0.6 mil.

After plating all coated parts, they are finally rinsed using de-ionizedwater.

In cemented tungsten carbides it has been found that binder metal may bepresent in a range of from about 1 to about 30 per cent by weight, andfor cemented titanium carbides the range of binder metal is from aboutto about 40 percent by weight.

It is within the contemplation of this invention that the binder metaland coating metal be one selected from Group VIII of the Periodic Table,and includes by way of example the metals Fe, Co, Ni, Pt, Ru, Rh, Pd andthe like. The preferred Group VIII metals is the group of Fe, Co and Ni.

It is also within the contemplation of this invention that in caseswherein the binder comprises mixed metals, such as Ni-Cu; Co-Mo-Cu;Fe-Ni-Cu, and the like, the coating is to consist essentially of theGroup VIII metal in the binder, and wherein there are two or more GroupVIII metals in the binder the coating is that Group VIII metal that ispresent in the predominant weight percent.

It is to be understood that various changes may be made in that whichhas been described, without departing from the spirit of the inventionor the scope of the appended claims.

What is claimed is:

1. A coated cemented carbide comprising, a cemented carbide comprising abinder metal selected from Group VIII metals, and a deposited wettablelayer coating on said cemented carbide, said coating consisting of thesame metal as the binder metal, whereby said coated cemented carbidefacilitates brazing.

2. The coated cemented carbide of claim 1, wherein the binder metal isone selected from the group consisting of iron, cobalt and nickel.

3. The coated cemented carbide of claim 2, wherein the cemented carbidecomprises a ttmgsten carbide and wherein the binder and coating arecobalt.

4. The coated cemented carbide of claim 2, wherein the cemented carbidecomprises titanium carbide and wherein the binder and coating arecobalt.

5. The coated cemented carbide of claim 2, wherein the cemented carbidecomprises titanium carbide and wherein the binder and coating arenickel.

6. The coated cemented carbide of claim 2, wherein the cemented carbidecomprises tungsten carbide and wherein the binder and coating arenickel.

7. A coated cemented carbide comprising a cemented carbide comprising abinder of more than one metal and wherein at least one of the metals isselected from Group VIII metals, and a deposited wettable layer coatingon said cemented carbide, said coating consisting of the same Group VIIImetal that is present in the predominant weight percent of the GroupVIII metals in the binder, whereby said coated cemented carbidefacilitates brazing.

8. The coated cemented carbide of claim 7, wherein at least one bindermetal is one selected from the group consisting of iron, cobalt andnickel.

9. The coated cemented carbide of claim 1, wherein the wettable layercoating is from about 0.0002 inch to about 0.0004 inch in thickness.

10. The coated cemented carbide of claim 7, wherein the wettable layercoating is from about 0.0002 inch to about 0.0004 inch in thickness.

1 1. The coated cemented carbide of claim 1, wherein said coated carbideis a cutting tip and wherein the thickness of the wettable layer coatingis from about 0.1 mil to about 0.6 mil.

12. The coated cemented carbide of claim 7, wherein said coated carbideis a cutting tip and wherein the thickness of the wettable layer coatingis from about 0.1 mil to about 0.6 mil.

1. A COATED CEMENTED CARBIDE COMPRISING A CEMENTED CARBIDE COMPRISING ABINDER METAL SELECTED FROM GROUP VIII METALS, AND A DEPOSITED WETTABLELAYER COATING ON SAID CEMENTED CARBIDE, SAID COATING CONSISTING OF THESAME METAL AS THE BINDER METAL WHEREBY SAID COATED CEMENTED CARBIDEFACILITATES BRAZING.
 2. The coated cemented carbide of claim 1, whereinthe binder metal is one selected from the group consisting of iron,cobalt and nickel.
 3. The coated cemented carbide of claim 2, whereinthe cemented carbide comprises a tungsten carbide and wherein the binderand coating are cobalt.
 4. The coated cemented carbide of claim 2,wherein the cemented carbide comprises titanium carbide and wherein thebinder and coating are cobalt.
 5. The coated cemented carbide of claim2, wherein the cemented carbide comprises titanium carbide and whereinthe binder and coating are nickel.
 6. The coated cemented carbide ofclaim 2, wherein the cemented carbide comprises tungsten carbide andwherein the binder and coating are nickel.
 7. A coated cemented carbidecomprising a cemented carbide comprising a binder of more than one metaland wherein at least one of the metals is selected from Group VIIImetals, and a deposited wettable layer coating on said cemented carbide,said coating consisting of the same Group VIII metal that is present inthe predominant weight percent of the Group VIII metals in the binder,whereby said coated cemented carbide facilitates brazing.
 8. The coatedcemented carbide of claim 7, wherein at least one binder metal is oneselected from the group consisting of iron, cobalt and nickel.
 9. Thecoated cemented carbide of claim 1, wherein the wettable layer coatingis from about 0.0002 inch to about 0.0004 inch in thickness.
 10. Thecoated cemented carbide of claim 7, wherein the wettable layer coatingis from about 0.0002 inch to about 0.0004 inch in thickness.
 11. Thecoated cemented carbide of claim 1, wherein said coated carbide is acutting tip and wherein the thickness of the wettable layer coating isfrom about 0.1 mil to about 0.6 mil.
 12. The coated cemented carbide ofclaim 7, wherein said coated carbide is a cutting tip and wherein thethickness of the wettable layer coating is from about 0.1 mil to about0.6 mil.